.shadow {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  background-color: rgba(0, 0, 0, 0.3);
}

.center {
  width: 400px;
  background-color: #fff;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  border-radius: 8px;
  padding: 10px;
  box-sizing: border-box;
}

footer {
  margin-top: 40px;
  text-align: right;
}

button {
  margin: 0 10px;
}